Electricity
Frequently Asked Questions
Electricity is the flow of electric charge (usually electrons) through a conductor due to a potential difference.
Electric current is the rate of flow of charge through a conductor.
Ampere (A).
A current of 1 A flows when 1 coulomb of charge passes through a conductor in 1 second.
\(( I = \frac{Q}{t} \) where \(I\) = current, \(Q\) = charge, \(t\) = time.
It is the work done to move a unit charge between two points in an electric circuit.
Volt (V).
\( V = \frac{W}{Q} \)
A device used to measure potential difference in a circuit.
Always in parallel with the component.
A device used to measure current in a circuit.
Always in series with the component.
Resistance is the opposition offered by a conductor to the flow of electric current.
Ohm (O).
At constant temperature, the current through a conductor is directly proportional to the potential difference across it: ( V \propto I ).
( V = IR )
Resistivity is a property of a material that defines how strongly it resists current flow.
Ohm-metre (Om).
\( R = \rho \frac{l}{A} \)
Power is the rate of consumption of electrical energy.
\( P = VI \), \( P = I^2 R \), \( P = \frac{V^2}{R} \)
Watt (W).
Power when 1 joule of energy is consumed in 1 second.
The total energy consumed by an electrical device.
Kilowatt-hour (kWh).
1 kWh = 1 unit of electricity.
A material that allows electric current to pass through it easily. (e.g., copper)
A material that does not allow current to pass through easily. (e.g., rubber)
Pictorial representation of an electric circuit using symbols.
Because it has low resistivity and high conductivity.
It is cheaper and lighter than copper.
A safety device that melts and breaks the circuit when excessive current flows.
So it melts quickly during overloading.
When live and neutral wires touch, causing very high current flow.
When too many appliances draw current simultaneously causing excessive current.
Circuits in which components are connected end-to-end in a single path.
Circuits in which components are connected across common points and have multiple paths.
To ensure each appliance gets the same voltage and works independently.
\( R = R_1 + R_2 + R_3 + \cdots\)
\( \frac{1}{R} = \frac{1}{R_1} + \frac{1}{R_2} +\cdots\)
Same current flows through all components.
Current divides based on resistance.
Parallel connection.
Heat produced is \( H = I^2 R t \).
Electric iron, toaster, heater.
Tungsten filament.
It has high melting point and high resistivity.
Production of chemical changes when current flows through a solution.
Production of magnetic field around a current-carrying conductor.
Heating effect of current.
Heating effect of current applied to heating coils.
Coulomb (C).
Average velocity of electrons under an electric field.
Atomic vibrations increase, obstructing electron flow.
They provide stable resistance and are cheap.
Copper, silver.
Nichrome.
A variable resistor used to regulate current.
A device that converts chemical energy into electrical energy.
Ampere (A), volt (V), ohm (O).
AC changes direction; DC flows in one direction.
They consume less power and produce more light.
To open or close the electric circuit.
When filament melts due to excessive heating.
A sudden flow of current through the human body.
Length, area, resistivity, and temperature.
Resistance increases.
Resistance decreases.
The property of conducting electric current.
Power consumed by an appliance when operated at rated voltage.
Geyser, heater, iron.
LED lamp, mobile charger.
\(100/1000 \times 10 = 1 \text{ kWh}\).
Failure of one appliance does not affect others.
To reduce heating losses.
Connecting metal body of appliances to earth for safety.
Prevents electric shock by offering low-resistance path to fault current.
An automatic switch that trips during overload or short circuit.
Measures electrical energy consumed by a household.
Units consumed × rate per unit.
\( P = I^{2} R \) heating loss in wires.
By using high voltage and low current.
Charge carried by 1 ampere current in 1 second.
To limit current and divide voltage in circuits.
Sudden break of high current path.
Voltage available at the terminals of a power source.
Due to \(I^2R\) heating effect.
Electric bell, motor.
Electroplating cell.
Device that consumes electrical energy.
It is expensive.
Circuit becomes short-circuited.
Prevent electric shock.
They contain free electrons.
Electromotive force — energy supplied per unit charge by a source.
Yes, EMF is total energy supplied; PD is energy used between points.
Fuse, MCB, earthing.
Increases with temperature.
Tungsten.
50 Hz.
220–240 V.
A device that measures voltage, current, and resistance.
Ratio of useful heat produced to electrical energy consumed.
High resistivity and high melting point.
Slow movement of electrons under electric field.
